Algebra and Sequences

Algebra and sequences appear regularly on the CSSE 11+ maths paper. The CSSE is known for pushing students beyond simple arithmetic — you may be asked to find unknown values, write expressions, and spot patterns in number sequences. This lesson covers all the algebra and sequence skills you need.

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What Is Algebra?

Algebra uses letters to stand for unknown numbers. Instead of writing "a number", we write a letter such as n, x, or a.

Expression	Meaning
3n	3 × n (three times n)
n + 7	n plus 7
2n - 4	Two times n, minus 4
n/5	n divided by 5
n²	n × n (n squared)

Remember: In algebra, we do not usually write the multiplication sign. We write 3n instead of 3 × n.

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Simplifying Expressions

To simplify, collect like terms — terms that contain the same letter.

Simplify: 4a + 3b + 2a - b